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[v3,1/6] powerpc: Add LKDTM accessor for patching addr

Message ID 20200827052659.24922-2-cmr@codefail.de
State New, archived
Headers show
Series Use per-CPU temporary mappings for patching | expand

Commit Message

Christopher M. Riedl Aug. 27, 2020, 5:26 a.m. UTC
When live patching a STRICT_RWX kernel, a mapping is installed at a
"patching address" with temporary write permissions. Provide a
LKDTM-only accessor function for this address in preparation for a LKDTM
test which attempts to "hijack" this mapping by writing to it from
another CPU.

Signed-off-by: Christopher M. Riedl <cmr@codefail.de>
 arch/powerpc/include/asm/code-patching.h | 4 ++++
 arch/powerpc/lib/code-patching.c         | 7 +++++++
 2 files changed, 11 insertions(+)
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diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h
index eacc9102c251..7216d6a6bb0a 100644
--- a/arch/powerpc/include/asm/code-patching.h
+++ b/arch/powerpc/include/asm/code-patching.h
@@ -187,4 +187,8 @@  static inline unsigned long ppc_kallsyms_lookup_name(const char *name)
 				 ___PPC_RA(__REG_R1) | PPC_LR_STKOFF)
 #endif /* CONFIG_PPC64 */
+unsigned long read_cpu_patching_addr(unsigned int cpu);
diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index 8c3934ea6220..85d3fdca9452 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -46,6 +46,13 @@  int raw_patch_instruction(struct ppc_inst *addr, struct ppc_inst instr)
 static DEFINE_PER_CPU(struct vm_struct *, text_poke_area);
+unsigned long read_cpu_patching_addr(unsigned int cpu)
+	return (unsigned long)(per_cpu(text_poke_area, cpu))->addr;
 static int text_area_cpu_up(unsigned int cpu)
 	struct vm_struct *area;